Remove the skin of sweet potatoes and cut into smaller pieces to quicken the steaming process. Steam sweet potatoes for at 10 minutes or until soft.
Allow the sweet potatoes to cool slightly. It should still be hot and you should be able to touch them without any discomfort from the excess heat. Mash the sweet potato using a fork. Mix in sugar. Then, add cornflour and tapioca flour to create a dough.
When the dough comes together, cut it into smaller chunks to create small balls. Each ball should weigh between 5 to 7g. Set aside.
Heat oil in a pan over low heat. Once the oil is heated, add the sweet potato balls. Fry them for about 2 minutes before increasing the heat to medium. Move the balls around during frying. Once the oil is heating up vigorously (as seen in the photo), use a fork to press each ball against the wall of the pan. The whole frying process should take about 6 minutes.